Molded plastic bottles and like containers are in widespread and continually expanding use for a wide variety of liquids, powders, granulates, and other diverse products. The resins used in these bottles and containers include high-density polyethylene, polypropylene, polyethylene terephthlate, and others. As in any other manufacturing process, there is likely to be considerable scrap created due to flaws in the bottles or other containers created during molding operations. Other containers must be scrapped when identifying labels, usually paper but frequently and increasingly plastic film, are misapplied. These problems are particularly apparent when in-mold labelling and decoration are utilized; it has been estimated that 3% to 5% of plastic bottles, as manufactured, are rejected. Furthermore, plastic bottles and like containers are seldom acceptable for reuse as is; virtually every sound plastic bottle becomes a scrap bottle when emptied of its contents.
Effective and economical reclamation of scrap plastic bottles has been achieved in some instances, even when label materials must be removed during reclaiming operations. Thus, effective reclamation of reject blow-molded polyethylene containers for laundry-household liquids with paper labels secured to the containers by a heat-sealed gel lacquer has been successfully accomplished, using dry mechanical impact procedures. Other reclamation processes have also been used.
The problems of reclamation of plastic bottles and like scrap articles, however, are materially exacerbated when each bottle is formed of two or more components, bonded to each other, the components being molded of different resins. This situation is perhaps best exemplified by beverage bottles now in common use, formed of molded polyethylene terephthlate bodies bonded to high density polyethylene bases. These beverage bottles usually have aluminum or polypropylene caps; their labels may comprise paper or plastic film, usually polypropylene. The conventional techniques used for plastic container reclamation, wet or dry, are not really efficient as applied to these bottles; in particular, they are not as effective as desirable in breaking down the bond between the components of the two different resins so that those resins can be separated for subsequent use. Other problems occur in connection with elimination or other acommodation of label and cap materials in the reclamation process.